But of mussels, the Ephesian ones, and those which resemble them, are, as to their juicy qualities, superior to the periwinkles, but inferior to the cockles; but they have more effect as diuretics than as aperients. But some of them are like squills, with a very disagreeable juice, and without any flavour; but there is a kind which is smaller than they are, and which are rough outside, which are more diuretic, and full of a more pleasant juice than the kind which resembles squills: but they are less nutritious, by reason of their sizes, and also because their nature is inferior. But the necks of the ceryces are exceedingly good for the stomach, and are not so nutritious as mussels and cockles and periwinkles; but for people who have a weak stomach, and who do not easily expel the food into the cavity of the bowels, they are useful, inasmuch as they do not easily turn on the stomach. For those things which are confessedly digestible are, on the contrary, very unwholesome for people of such a constitution, being very easily inclined to turn on the stomach, because they are tender and easily dissolved. On which account the bags containing their entrails are not suited to vigorous stomachs, but they are very good for those whose bowels are in a weak state. But what are more nutritious than the others, and far nicer in taste, are the entrails of the purple-fish; though they certainly are somewhat like the squill. For indeed all shell-fish are of the same character; but the purple-fish and the solen have this peculiar characteristic, that if they are boiled they yield a thick juice. But the necks of the purple-fish, when boiled by themselves, are exceedingly good for bringing the stomach into a good condition. And Posidippus speaks of them in his Locrians in these terms:-- It is time now to eat eels and crabs, Cockles, and fresh sea-urchins, and fish sounds, And pinnas, and the necks of fish, and mussels.